Spark plug



' May 12, 1925.

w. w. WOODROOF SPARKPLUG Filed April 6, 1923 INVENTOR W. W. Wood r0 of,

WITNESSES BY 5 i ATTORNEYS Patented May 12, 1925.

UNITED STATES WILLIAM WALTON WOODROOF, OF AUBURN, ALABAMA.

SPARK PLUG.

Application filed April 6,

To all whom 2'75 may concern l3-e it known that I, WILLIAM lViaL'roN \Vooonoor, a citizen of the United States, and a resident of Auburn, in the county of Lee and State of Alabama, have invented certain new and useful Improvements in Spark Plugs, of which the following is a specification.

My invention relates to improvements in spark plugs and it consists of the constructions, combinations, and mode of operation herein described and claimed.

An object of the invention to provide a spark plug in which the only metal exposed on the inside of the cylinder is that contained by the electrodes, the other parts of the spark plug consisting of glazed porcelain upon which practically no carbon will collect.

Other objects and advantages will appear in the following specification, reference be ing had to the accompanying drawing. in which:

Fig. 1 is a longitudinal section of a spark plug constructed in accordance with the invention, parts of the spark plug being shown in elevation,

Fig. 2 is'a side elevation of the core of the spark plug, the petticoat being shown in dotted lines,

Fig. 3 is a detail sectional view of the petticoat, and

Fig. 4tis a side elevation of the metallic base which carries the outer electrodes and upon which the other parts of the spark plug are mounted.

One of the foremost purposes in designing the spark plug in the particular manner disclosed herein, is to expose only so much metal as is absolutely necessary. The rest of the exposed parts of the spark plug consist of glazed porcelain. The porcelain, due to the glaze, will resist the ready accumulation of carbon. It is well known that spark plugs having considerable metallic surfaces ex posed to the interior of the cylinder readily become clogged with carbon. This necessitates ,taking the plug out and removing the carbon.

According to the drawing, the improved spark plug comprises a core 1 through the center of which the central electrode 2 extends. This electrode is fastened in place in any suitable manner, it being provided with a suitable form of wire binding 3 at the top. A relatively small portion of the central 1923. Serial No. 830,301.

electrode projects beyond the lower oxtre1nity of the core 1.

A series of concentric steps 4- begin at the bottom of the core 1 and become progressively larger toward the place 5 where the petticoat 6 joins the core. The inside of the petticoat presents a smooth surface 7 which slightly slants toward the lower rim. The steps serve to niateriaily increase the exposed area of the spark plug. As intimated above, both the core 1 and petticoat 6 are made of porcelain. The exposed surfaces are glazed, this Jeing true of the outside of the petticoat, as well as the inside. In view of the fact that the inner surfaces are extended by virtue of the steps the accumulation of carbon will not occur as readily as it would were the exposed surface smaller.

As a matter of fact, the glaze of the porcelain is intended to discourage the accumulation of carbon, and as stated before, this is one of the purposes of the invention. The core 1 and petticoat 6 are carried by the base 8. This base is made of metal and carries the outer electrode 9 which is bent in respect to the central electrode 2 to form a spark end, as is customary. The base 8 has threads 10 by means of which it. is screwed into the cylinder. None of the base 8 is exposed to the inside of the cylinder, excepting the narrow rim at the lower edge of the threads. Therefore, no metal, excepting this narrow rim and the metal in the exposed part of the electrodes can be subject to carbonization.

A central enlargement 11 on the core 1 makes provision for tight joints. One of these occurs where the enlargement bears on a gasket 12 in the recessed part 13 of the base 8. Another occurs at the gasket H where the jam nut '15 bears down. This jam nut is screwed into the threaded part of the recess 13. lVhen the jam nut is tightened, gastight joints are provided around the core 1.

It is to be noted that the upper edge of the pedestal 6 extends slightly above the ronnded portion 16 of the recess 13, providing a space or chamber for the gasket 12-. It is also to be noted that the upper end of the petticoat 6 is beveled at 1?. This bevel is in substantial continuation of the general inclination of the gasket 12, and provides a very close seat for the correspomling portion 18 of the core 1.

In manufacturing the spark plug. it is optional whether the petticoat 6 be molded integral with the core 1, or whether it be fore, it is repeated, that it is merely a matter of choice in the manufacture of the plug whether the petticoat be made integral with the-core in the first place or whether it be; ce-

mented on afterwards. j

lVhile the construction and arrangement of the improved spark plug as herein described and claimed, is that of a generally preferred form, obviously modifications and changes may be made without departing from the spirit of the invention or'the scope of the claims.

I claim A spark plug comprising a base having an externally threaded portion and having a reit will same dose partially threaded and merging into a rounded portion-,- a porcelain pettioat fitted to provide a chamber, a porcelain coremounte'd in the basehaving an enlargement situated in said recess and having a portion engaging the bevel of said petticoat to produce a tight joint, said core having a series of concentric steps reducing the core out wardlyof the sp'ark plug, a gasket occupying said chamber and being engaged by said enlargement, a jamb nut screwed into the threaded recess and pressing upon said enlargement, a gasket interposed between the jamb nut and said enlargement, and electrodes carried both by the core and by the base.

WILLIAM WALTON NOODROOF.

1e internal surface slop- 

